Electrically operated equipment, i.e. electronic equipment or electrical power equipment, is installed both in outdoor and indoor environments. In both of these environmental situations, it has been found to be convenient and, perhaps, prudent to provide visual indications to show whether the equipment, or parts thereof, are operating correctly and effectively. If properly monitored, visual indicators will inform maintenance technicians immediately when any malfunction of equipment occurs. Visual indicators are used to identify a particular item of equipment which is malfunctioning, as distinct from those which remain functional. Such identification enables necessary repairs or equipment replacement to be effected as soon as possible and with minimal operational downtime. Hence, any customer provided with service by such equipment, e.g. telecommunication service, is indisposed for as short a time as possible by lack of this service due to malfunction.
Visual indication is appropriately provided by an illumination process, e.g. with the use of a light emitting diode (LED) so as to be readily seen as required. Particularly with the use of visual indicators on outside plant equipment, problems are known to arise because of environmental conditions. Illuminated visual indicators protrude through apertures in equipment housings and these apertures, unless properly sealed, allow the surrounding environmental conditions to reach the equipment and detrimentally affect the operation. Thus, the operational parts of equipment, e.g. printed circuit boards, and electrical terminals, may be subjected to humidity conditions in the form of airborne mist or heat condensed droplets of water. Precipitation in any form, especially when wind driven, and extreme temperature changes also may cause operational problems.
In known structures, with LEDs protruding through apertures in housings, the LEDs are either mounted upon printed circuit boards or are connected thereto by electric conductors. The LEDs typically are covered with clear plastic layers or windows, or with glass lens caps. Sealing always presents problems around LEDs mounted in such ways. Sealing is necessary around the covers of the LEDs to prevent moisture ingress into housings. Sealing may also be necessary to prevent electromagnetic or radio frequency transmission into and out of housings with resultant detrimental effects on the operation of equipment both within the housing and outside the housing. Where satisfactory sealing is initially effected with such structures, there is always the possibility of sealing failure during usage, particularly when subjected to outside environmental conditions.
In addition, some structures may be for use underground. For such usage, sealing must be adequate to prevent water ingress when submerged in water and also to withstand extremes of water pressure when water depth increases.
Attempts have been suggested to avoid sealing problems. One suggested attempt involves the incorporation of an LED into an environmentally sealed planar carrier. The LED, circuitry to the LED and the carrier being referred to as a “membrane switch”. However, while the LED and circuitry within the switch may be effectively sealed, the switch needs to be mounted upon a housing of equipment with which it is associated and is connected by an electric conductor through the housing to circuitry of the equipment. Problems may exist with sealing an aperture in the housing surrounding the conductor and with sealing the switch to the housing. Also, such sealing may be unreliable after a period of usage especially in outdoor environmental conditions.
It follows that sealing failure may result in malfunction and deterioration in circuitry operation with also the possibility of allowing leaking of electromagnetic and radio frequency transmission through the housing.